Continuous method for the production of a pigment masterbatch

A method for the production of a pigment masterbatch by extrusion, comprising the steps of:

• a) metering continuously, a thermoplastic polymer in granular or powder form into a twin-screw extruder;
• b) melting the polymer in the extruder to form a molten polymer;
• c) metering, continuously, a pumpable pigment press cake containing pigment, water and/or organic solvent into the molten polymer through an inlet port of the extruder under elevated pressure, the pressure being sufficiently high that the boiling point of the water and/or organic solvent is higher than the internal temperature of the extruder in the region of the inlet port;
• d) optionally, adding a flow improver;
• e) dispersing the pigment into the molten polymer from the press cake by the action of shear forces;
• f) removing the water and/or organic solvent though at least one outlet port of the extruder, under elevated pressure, the pressure being sufficiently high that the boiling point of the water and/or organic solvent is higher than the internal temperature of the extruder in the region of the at least one outlet port to a form a pigmented polymer melt;
• and
• g) discharging the pigmented polymer melt from the extruder
• h) cooling the pigmented polymer melt to form a pigmented polymer;
• and
• i) granulating the pigmented polymer.